The present invention relates to a stent prosthesis for vascular surgery, in particular to a stent prosthesis for bridging a vascular enlargement in the area of the aortic arch, i.e. for example immediately at, close to, or at a certain distance to the aortic arch.
For many years, stents, also known as stent prostheses or stent implants, have been used in vascular surgery, radiology and heart surgery for eliminating aortic aneurysms. Such a stent prosthesis represents a tubular stent body comprising a sheathing made from a generally liquid-proof material, in particular synthetic material which is flexibly pliable and radially expandable. Such stent body is inserted through the artery and placed at the location of treatment in a radially folded state in an insertion tube, for example of a catheter, and is released by the catheter at the location of treatment so that the stent body is expanded or unfolded and attaches itself close to the vascular wall at least with its front end portion and rear end portion during insertion, in particular in front of and behind the vascular enlargement. In the sheathing wall of the stent body, a wire grating material or braided wire is generally provided, which radially expands due to its own elasticity, when the stent body is pushed out of the insertion tube of the catheter for the purpose of releasing the stent, or when the insertion tube is withdrawn for the purpose of releasing the stent, or when the stent body is expanded—for example by means of a balloon catheter.
The folded stent is for example inserted through a cut in the skin of the groin via the artery located underneath, placed in the aorta and is unfolded there in such a manner that the vascular enlargement or sac is entirely bypassed or eliminated. For this purpose it is necessary for the stent to be safely anchored before and after sacculation and for it to seal in such a manner that no more direct blood flow to the sac is possible. This is effected while the blood flows and during x-ray radiation, which makes an accurate alignment complicated.
A special difficulty exists in the area of the thoracic aorta, particularly in cases in which the arm supplying artery or the carotid artery is partially or completely covered where it branches off the aorta. Entirely blocked vital lateral rami also might have to be treated by means of a bypass procedure. A precondition, however, is that at least one of the main lateral arteries branching off the aortic arch (truncus brachio-cephalicus) remains open. It is even more difficult to position a lateral opening in the stent prosthesis, which needs to be placed very accurately, in front of the site where it branches off the lateral ramus (for example truncus brachio-cephalicus) so that blood flow in the respective artery is allowed. A blocking of this artery would cause severe complications. An accurate placing of the stent is further impeded by the curved course of the thoracic aorta at the aortic arch.
EP 0 894 481 A2 describes a long marker thread made from or with a material recognizable during x-ray treatment, attached alongside, for example, the plaited outer jacket of the stent body in such a manner that the place and position of the stent body may be detected under an x-ray radiation by means of the marker thread while inserting and placing the stent body in the artery. Such marker thread, the proximal thread end of which is for example fixed in the insertion catheter, is attached to the stent body in such a manner that it can be pulled out of the stent body after positioning the stent body. It is also possible that fixedly attached marker threads are provided, for example knotted ones, which permanently remain on the stent body and which do not significantly extend away from the stent body.